An image-forming device disclosed in Japanese Patent Application Publication No. 2006-72285 employs an electrophotographic system. The image-forming device has a developing cartridge that is configured to be detachably mounted in a device body for supplying developer to a photosensitive drum.
One such developing cartridge that has been proposed is provided with a developing roller that carries toner, a supply roller that supplies toner to the developing roller, and a collar member that covers and is electrically connected to a developing-roller shaft of the developing roller and a supply-roller shaft of the supply roller.
This developing cartridge is mounted in the device body of the image-forming device after being mounted in a drum cartridge having the photosensitive drum.